scholarly journals Speciation and gene flow across an elevational gradient in New Guinea kingfishers

2019 ◽  
Author(s):  
Ethan Linck ◽  
Benjamin G. Freeman ◽  
John P. Dumbacher
Keyword(s):  
Gene Flow ◽  
Nuclear Dna ◽  
New Guinea ◽  
Ecological Speciation ◽  
High Elevation ◽  
Divergent Selection ◽  
Secondary Contact ◽  
Gene Trees ◽  
Tropical Mountains

AbstractClosely related species with parapatric elevational ranges are ubiquitous in tropical mountains worldwide. The gradient speciation hypothesis proposes that these series are the result of in situ ecological speciation driven by divergent selection across elevation. Direct tests of this scenario have been hampered by the difficulty inferring the geographic arrangement of populations at the time of divergence. In cichlids, sticklebacks, and Timema stick insects, support for ecological speciation driven by other selective pressures has come from demonstrating parallel speciation, where divergence proceeds independently across replicated environmental gradients. Here, we take advantage of the unique geography of the island of New Guinea to test for parallel gradient speciation in replicated populations of Syma kingfishers that show extremely subtle differentiation across elevation and between historically isolated mountain ranges. We find that currently described high elevation and low elevation species have reciprocally monophyletic gene trees and form nuclear DNA clusters, rejecting this hypothesis. However, demographic modeling suggests selection has likely maintained species boundaries in the face of gene flow following secondary contact. We compile evidence from the published literature to show that while in situ gradient speciation in labile organisms such as birds appears rare, divergent selection and post-speciation gene flow may be an underappreciated force in the origin of elevational series and tropical beta diversity along mountain slopes.

scholarly journals Ecological Divergence and the Origins of Intrinsic Postmating Isolation with Gene Flow

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Aneil F. Agrawal ◽  
Jeffrey L. Feder ◽  
Patrik Nosil
Keyword(s):  
Linkage Disequilibrium ◽  
Gene Flow ◽  
Natural Selection ◽  
Theoretical Models ◽  
Ecological Speciation ◽  
Divergent Selection ◽  
Postmating Isolation ◽  
Divergent Natural Selection ◽  
Mathematical Exploration ◽  
Neutral Gene

The evolution of intrinsic postmating isolation has received much attention, both historically and in recent studies of speciation genes. Intrinsic isolation often stems from between-locus genetic incompatibilities, where alleles that function well within species are incompatible with one another when brought together in the genome of a hybrid. It can be difficult for such incompatibilities to originate when populations diverge with gene flow, because deleterious genotypic combinations will be created and then purged by selection. However, it has been argued that if genes underlying incompatibilities are themselves subject to divergent selection, then they might overcome gene flow to diverge between populations, resulting in the origin of incompatibilities. Nonetheless, there has been little explicit mathematical exploration of such scenarios for the origin of intrinsic incompatibilities during ecological speciation with gene flow. Here we explore theoretical models for the origin of intrinsic isolation where genes subject to divergent natural selection also affect intrinsic isolation, either directly or via linkage disequilibrium with other loci. Such genes indeed overcome gene flow, diverge between populations, and thus result in the evolution of intrinsic isolation. We also examine barriers to neutral gene flow. Surprisingly, we find that intrinsic isolation sometimes weakens this barrier, by impeding differentiation via ecologically based divergent selection.

Playbacks revisited: asymmetry in behavioural response across an acoustic boundary between two parapatric bird species

Behaviour ◽  
2015 ◽  
Vol 152 (14) ◽  
pp. 1933-1951 ◽  
Author(s):  
Tamsin Burbidge ◽  
Thari Parson ◽  
Paula C. Caycedo-Rosales ◽  
Carlos Daniel Cadena ◽  
Hans Slabbekoorn
Keyword(s):  
Gene Flow ◽  
Response Pattern ◽  
Bird Species ◽  
Elevational Gradient ◽  
High Elevation ◽  
Secondary Contact ◽  
Potential Contribution ◽  
Asymmetric Response ◽  
Singing Style ◽  
The Impact

Behavioural barriers to gene flow can play a key role in speciation and hybridisation. Birdsong is well-known for its potential contribution to such behavioural barriers as it may affect gene flow through an effect on territorial and mating success across population boundaries. Conspecific recognition and heterospecific discrimination of acoustic variation can prevent or limit hybridization in areas where closely related species meet. Here we tested the impact of song differences on territorial response levels between two adjacent Henicorhina wood-wren species along an elevational gradient in Colombia. In an earlier study, playback results had revealed an asymmetric response pattern, with low-elevation H. leucophrys bangsi responding strongly to any conspecific or heterospecific song variant, whereas high-elevation H. anachoreta birds discriminated, responding more strongly to their own songs than to those of bangsi. However, in that study we could not exclude a role for relative familiarity to the song stimuli. In the current study we confirm the asymmetric response pattern with song stimuli recorded close to and on both sides of the distinct acoustic boundary. Furthermore, we also show a previously unnoticed divergence in singing style between these two wood-wren species, which may contribute to an acoustically guided barrier to hybridization in this secondary contact zone.

scholarly journals Asymmetric Reproductive Barriers and Gene Flow Promote the Rise of a Stable Hybrid Zone in the Mediterranean High Mountain

2021 ◽  
Vol 12 ◽  
Author(s):  
Mohamed Abdelaziz ◽  
A. Jesús Muñoz-Pajares ◽  
Modesto Berbel ◽  
Ana García-Muñoz ◽  
José M. Gómez ◽  
...  
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Sierra Nevada ◽  
Hybrid Zone ◽  
High Elevation ◽  
Secondary Contact ◽  
High Mountain ◽  
Hybrid Zones ◽  
Reproductive Barriers ◽  
Sierra Nevada Mountains

Hybrid zones have the potential to shed light on evolutionary processes driving adaptation and speciation. Secondary contact hybrid zones are particularly powerful natural systems for studying the interaction between divergent genomes to understand the mode and rate at which reproductive isolation accumulates during speciation. We have studied a total of 720 plants belonging to five populations from two Erysimum (Brassicaceae) species presenting a contact zone in the Sierra Nevada mountains (SE Spain). The plants were phenotyped in 2007 and 2017, and most of them were genotyped the first year using 10 microsatellite markers. Plants coming from natural populations were grown in a common garden to evaluate the reproductive barriers between both species by means of controlled crosses. All the plants used for the field and greenhouse study were characterized by measuring traits related to plant size and flower size. We estimated the genetic molecular variances, the genetic differentiation, and the genetic structure by means of the F-statistic and Bayesian inference. We also estimated the amount of recent gene flow between populations. We found a narrow unimodal hybrid zone where the hybrid genotypes appear to have been maintained by significant levels of a unidirectional gene flow coming from parental populations and from weak reproductive isolation between them. Hybrid plants exhibited intermediate or vigorous phenotypes depending on the analyzed trait. The phenotypic differences between the hybrid and the parental plants were highly coherent between the field and controlled cross experiments and through time. The highly coherent results obtained by combining field, experimental, and genetic data demonstrate the existence of a stable and narrow unimodal hybrid zone between Erysimum mediohispanicum and Erysimum nevadense at the high elevation of the Sierra Nevada mountains.

scholarly journals Theoretical Expression for the Evolution of Genomic Island of Speciation: From Its Birth to Preservation

2019 ◽  
Author(s):  
T. Sakamoto ◽  
H. Innan
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Genetic Divergence ◽  
Genomic Island ◽  
Evolutionary Process ◽  
Ecological Speciation ◽  
Divergent Selection ◽  
Genomic Islands ◽  
Theoretical Expression ◽  
Locally Adaptive

AbstractEcological speciation could be driven by divergent selection that works to maintain phenotypes that are adaptive to each niche. In its early stages, genetic divergence (or FST) can be maintained around the target sites of divergent selection, while in other regions, genetic variation can be mixed by gene flow or migration. Such regions of elevated genetic divergence are called genomic islands of speciation. In this work, we theoretically consider the evolutionary process of a genomic island of speciation, from its birth to stable preservation. Under a simple two-population model, we use a diffusion approach to obtain analytical expressions for the probability of initial establishment of a locally adaptive allele, the reduction of genetic variation due to the spread of the adaptive allele, and the process to the development of a sharp peak of divergence. Our result would be useful to understand how genomes evolve through ecological speciation with gene flow.

scholarly journals Origin of elevational replacements in a clade of nearly flightless birds – most diversity in tropical mountains accumulates via secondary contact following allopatric speciation

2019 ◽  
Author(s):  
Carlos Daniel Cadena ◽  
Laura N. Céspedes
Keyword(s):  
Species Turnover ◽  
Secondary Contact ◽  
Elevational Gradients ◽  
Closely Related Species ◽  
Tropical Mountains ◽  
Limited Dispersal ◽  
Phylogenetic Framework ◽  
Parapatric Speciation ◽  
The Tropics

AbstractTropical mountains are biodiversity hotspots. In particular, mountains in the Neotropics exhibit remarkable beta diversity reflecting species turnover along elevational gradients. Elevational replacements of species have been known since early surveys of the tropics, but data on how such replacements arise are scarce, limiting our understanding of mechanisms underlying patterns of diversity. We employed a phylogenetic framework to evaluate hypotheses accounting for the origin of elevational replacements in the genusScytalopus(Rhinocryptidae), a speciose clade of passerine birds with limited dispersal abilities occurring broadly in the Neotropical montane region. We found that species ofScytalopushave relatively narrow elevational ranges, closely related species resemble each other in elevational distributions, and most species replacing each other along elevational gradients are distantly related to each other. Although we cannot reject the hypothesis that a few elevational replacements may reflect parapatric speciation along mountain slopes, we conclude that speciation inScytalopusoccurs predominantly in allopatry within elevational zones, with most elevational replacements resulting from secondary contact of formerly allopatric lineages. Our study suggests that accumulation of species diversity in montane environments reflects colonization processes as opposed toin situdivergence even in dispersal-limited animals.

scholarly journals Pervasive Genomic Signatures of Local Adaptation to Altitude Across Highland Specialist Andean Hummingbird Populations

2021 ◽  
Author(s):  
Marisa C W Lim ◽  
Ke Bi ◽  
Christopher C Witt ◽  
Catherine H Graham ◽  
Liliana M Dávalos
Keyword(s):  
Gene Flow ◽  
Local Adaptation ◽  
Genetic Drift ◽  
Population Genetic ◽  
Environmental Gradients ◽  
Functional Differentiation ◽  
High Elevation ◽  
Nucleotide Polymorphisms ◽  
Peruvian Andes ◽  
Tropical Mountains

Abstract Populations along steep environmental gradients are subject to differentiating selection that can result in local adaptation, despite countervailing gene flow, and genetic drift. In montane systems, where species are often restricted to narrow ranges of elevation, it is unclear whether the selection is strong enough to influence functional differentiation of subpopulations differing by a few hundred meters in elevation. We used targeted capture of 12 501 exons from across the genome, including 271 genes previously implicated in altitude adaptation, to test for adaptation to local elevations for 2 highland hummingbird species, Coeligena violifer (n = 62) and Colibri coruscans (n = 101). For each species, we described population genetic structure across the complex geography of the Peruvian Andes and, while accounting for this structure, we tested whether elevational allele frequency clines in single nucleotide polymorphisms (SNPs) showed evidence for local adaptation to elevation. Although the 2 species exhibited contrasting population genetic structures, we found signatures of clinal genetic variation with shifts in elevation in both. The genes with SNP-elevation associations included candidate genes previously discovered for high-elevation adaptation as well as others not previously identified, with cellular functions related to hypoxia response, energy metabolism, and immune function, among others. Despite the homogenizing effects of gene flow and genetic drift, natural selection on parts of the genome evidently optimizes elevation-specific cellular function even within elevation range-restricted montane populations. Consequently, our results suggest local adaptation occurring in narrow elevation bands in tropical mountains, such as the Andes, may effectively make them “taller” biogeographic barriers.

scholarly journals Developmental rate: A unifying mechanism for sympatric divergence in postglacial fishes?

2012 ◽  
Vol 58 (1) ◽  
pp. 21-34 ◽  
Author(s):  
Megan V. Mcphee ◽  
David L. G. Noakes ◽  
Fred W. Allendorf
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Genetic Recombination ◽  
Rapid Evolution ◽  
Developmental Rate ◽  
Ecological Speciation ◽  
Divergent Selection ◽  
Fish Populations ◽  
Trophic Polymorphism ◽  
Individual Traits

Abstract Morphologically divergent ecotypes arise in fish populations on postglacial time scales, and resource polymorphisms are often invoked to explain their origin. However, genetic recombination can constrain the ability of divergent selection to produce reproductive isolation in sympatry. Recombination breaks up favorable combinations of traits (“adaptive suites”) if individual traits are affected by different loci. Recombination also breaks up any association between traits under divergent selection and traits contributing to reproductive isolation. Thus, ecological speciation in the absence of preexisting barriers to gene flow is more likely when pleiotropy minimizes the number of loci involved. Here, we revisit research conducted by Carl Hubbs in the early 1900s on the effects of developmental rate on morphological traits in fishes. Hubbs’ work provides a mechanism to explain how sympatric divergence by trophic polymorphism can occur despite the challenges of recombination. We consider the implications of Hubbs’ observations for ecological speciation with gene flow in fishes, as well as rapid evolution in captive fish populations.

scholarly journals Geographic Structure of Mitochondrial and Nuclear Gene Polymorphisms in Australian Green Turtle Populations and Male-Biased Gene Flow

Genetics ◽  
1997 ◽  
Vol 147 (4) ◽  
pp. 1843-1854 ◽  
Author(s):  
Nancy N FitzSimmons ◽  
Craig Moritz ◽  
Colin J Limpus ◽  
Lisa Pope ◽  
Robert Prince
Keyword(s):  
Gene Flow ◽  
Genetic Structure ◽  
Green Turtle ◽  
Nuclear Dna ◽  
Nuclear Gene ◽  
Chelonia Mydas ◽  
Single Copy ◽  
Microsatellite Data ◽  
Ecological Data ◽  
Infinite Allele Model

Abstract The genetic structure of green turtle (Chelonia mydas) rookeries located around the Australian coast was assessed by (1) comparing the structure found within and among geographic regions, (2) comparing microsatellite loci vs. restriction fragment length polymorphism analyses of anonymous single copy nuclear DNA (ascnDNA) loci, and (3) comparing the structure found at nuclear DNA markers to that of previously analyzed mitochondrial (mtDNA) control region sequences. Significant genetic structure was observed over all regions at both sets of nuclear markers, though the microsatellite data provided greater resolution in identifying significant genetic differences in pairwise tests between regions. Inferences about population structure and migration rates from the microsatellite data varied depending on whether statistics were based on the stepwise mutation or infinite allele model, with the latter being more congruent with geography. Estimated rates of gene flow were generally higher than expected for nuclear DNA (nDNA) in comparison to mtDNA, and this difference was most pronounced in comparisons between the northern and southern Great Barrier Reef (GBR). The genetic data combined with results from physical tagging studies indicate that the lack of nuclear gene divergence through the GBR is likely due to the migration of sGBR turtles through the courtship area of the nGBR population, rather than male-biased dispersal. This example highlights the value of combining comparative studies of molecular variation with ecological data to infer population processes.

scholarly journals Assessment of MERRA-2 and ERA5 to Model the Snow Water Equivalent in the High Atlas (1981–2019)

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 890
Author(s):  
Mohamed Wassim Baba ◽  
Abdelghani Boudhar ◽  
Simon Gascoin ◽  
Lahoucine Hanich ◽  
Ahmed Marchane ◽  
...  
Keyword(s):  
River Discharge ◽  
Snow Water Equivalent ◽  
High Elevation ◽  
Water Runoff ◽  
High Atlas ◽  
Seasonal Snow ◽  
Snow Covered Area ◽  
Covered Area ◽  
Snow Water

Melt water runoff from seasonal snow in the High Atlas range is an essential water resource in Morocco. However, there are only few meteorological stations in the high elevation areas and therefore it is challenging to estimate the distribution of snow water equivalent (SWE) based only on in situ measurements. In this work we assessed the performance of ERA5 and MERRA-2 climate reanalysis to compute the spatial distribution of SWE in the High Atlas. We forced a distributed snowpack evolution model (SnowModel) with downscaled ERA5 and MERRA-2 data at 200 m spatial resolution. The model was run over the period 1981 to 2019 (37 water years). Model outputs were assessed using observations of river discharge, snow height and MODIS snow-covered area. The results show a good performance for both MERRA-2 and ERA5 in terms of reproducing the snowpack state for the majority of water years, with a lower bias using ERA5 forcing.

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